Carbon Sequestration Capacity Research Articles

Current research hotspots and frontier trends on carbon budget of coastal wetlands: A bibliometric analysis

ABSTRACT Coastal wetlands are the main distribution of blue carbon in coastal zones and well known for their high carbon sequestration capacity. Investigating the variation of carbon budget is crucial for understanding the functionality of coastal wetlands and effectively addressing climate change. In this study, a bibliometric analysis of 4,509 articles was conducted to reveal research progress, hot issues, and emerging trends in the coastal wetland carbon budget field. The number of publications and citations in this field increased exponentially from 1991 to 2022. The leading subject category was Environmental Sciences with 1,844 articles (40.9%). At present, studies have been focused on blue carbon, the effects of climate change and man-made disturbances on carbon cycle, and the restoration of coastal wetlands. Based on the hotspots and trends in this field, the future researches should include (1) exploring the functional mechanisms of various factors affecting carbon cycle and establishing a methodological system for the estimation of blue carbon in coastal wetlands; (2) researching restoration techniques of coastal wetland and constructing wetland restoration evaluation index system; and (3) formulating enforceable carbon trading policy and strengthening international cooperation.

Estimation of potential carbon sequestration in Thai reforestation from mining, based on the integrated spatial analysis

Mining, an activity that dates to the earliest stages of human civilization, has played a vital role in fulfilling human requirements for an extended period of time. Nevertheless, it is worth noting that this particular activity accounts for a significant proportion, ranging from 4% to 7% of the overall world greenhouse gas emissions. These emissions mostly consist of carbon dioxide, methane, and nitrogen oxides, which are released because of fuel burning, on-site energy generation, and many other sources. The mining industry, as a constituent of industrial process and product use (IPPU) sector in Thailand, makes a substantial contribution to these emissions. Thailand is now engaged in the implementation of carbon sequestration strategies, specifically focusing on the reclamation and replanting of post-mining zones. This initiative aims to tackle the various issues associated with small-scale operations within the country’s mining sector. The objective of this study is to analyse the carbon sequestration potential of Thailand’s mining area through the utilization of satellite pictures obtained from LANDSAT 8 OLI and Geographic Information System (GIS) applications. This study assesses the present carbon storage capacity, establishes the appropriate carbon pricing, and investigates the potential for reforestation in mining areas inside the nation. Based on the findings, it is evident that the northern region of Thailand has the most substantial potential for carbon sequestration, mostly due to the presence of vegetated land. Furthermore, it is projected that the overall carbon sequestration capacity in Thailand will amount to 14.68 MtCO2e in 2023 and 28.02 MtCO2e in 2030.

Returning Cropland to Grassland as a Potential Method for Increasing Carbon Storage in Dry-Hot Valley Areas

A key aspect of mitigating global climate warming is enhancing the carbon storage capacity of terrestrial ecosystems. China’s Grain for Green Program (GFGP) is the largest ecological restoration project in the world, which is closely associated with land use change. A systematic assessment of the GFGP’s impact on regional carbon storage is of great significance for promoting regional development and maintaining ecosystem stability. Therefore, this study selects a typical dry-hot valley area—Yanjin County—as the study area, which serves as an ecological protection barrier in Southwest China. We employed the InVEST model and Geo-detector model based on land use data from three periods (2000, 2014, and 2019), combined with static overlay analysis methods, in order to evaluate the impact of the implementation of GFGP on the spatial and temporal distribution of carbon storage. We also explored the driving factors of the spatial differentiation of carbon storage. The results indicate that, since the implementation of the GFGP, a total of 180.03 km2 of cropland has been converted to forestland, increasing the forest cover rate from 81.83% to 83.37%. The project has contributed 5.88 × 105 t to regional carbon storage, effectively offsetting carbon emissions caused by human activities such as urban expansion while also promoting the growth of regional carbon storage. The implementation of the GFGP has led to changes in three types of land use. Among them, converting cropland to forestland (3262 t/km2) is the most effective carbon sequestration method, and converting cropland to grassland (2530 t/km2) has shown great potential in carbon sequestration. Additionally, the study found that elevation (0.038–0.059) is the main factor affecting the spatial differentiation of carbon storage, and the interaction between elevation and other factors can effectively enhance the carbon sequestration capacity of regional ecosystems. Overall, the GFGP not only plays a significant role in combating climate warming but also makes an important contribution to improving the stability and sustainability of regional ecosystems.

Comprehensive evaluation and application of woody plants in the green spaces of parks in saline-Alkaline areas from a low-carbon perspective: A case study of Tianjin Qiaoyuan Park.

The field of landscape architecture has placed significant emphasis on low-carbon landscapes due to the increasing challenges posed by global warming and environmental deterioration in recent years. The soil ecological conditions in saline-alkaline areas are characterized by poor quality, resulting in suboptimal growth conditions for trees. This, in turn, hampers their ability to effectively sequester carbon, thereby diminishing the potential benefits of carbon sinks. Additionally, the maintenance of tree landscapes in such areas generates more carbon emissions than does conventional green land, making it difficult to reap the benefits of tree-based carbon. A comprehensive evaluation of trees in green park spaces in saline-alkaline areas is conducted from a low-carbon perspective; by identifying the dominant tree species that are well suited to greening, we can offer a precise scientific foundation for implementing low-carbon greening initiatives in cities situated in saline-alkaline environments. Therefore, as a case study, this study investigates Tianjin Qiaoyuan Park, a typical saline park in the Bohai Bay region. The hierarchical analysis method (AHP) was used to evaluate 50 species of trees and shrubs in the park from a low-carbon perspective. The results show that the evaluation system consists of four criterion layers and 15 indicator factors. The relative weight of the criterion layer followed the order of habitat adaptability (B2) > carbon sequestration capacity (B1) > low-carbon management and conservation (B3) > landscape aesthetics (B4). The indicator layer assigned greater weight values to net assimilation (C1), saline and alkaline adaptability (C3), drought tolerance (C4), irr igation and fertilization needs (C8), growth rate (C2), and adaptability to barrenness (C5). The trees were classified into five distinct categories, with each exhibiting significant variation in terms of the strengths and weaknesses of the indicators. According to the comprehensive score, the trees were categorized into three levels. The Grade I plants exhibited the best carbon efficiency performance, comprising a total of 12 species (e.g. Sabina chinensis, Fraxinus chinensis 'Aurea' and Hibiscus syriacu), and demonstrated superior performance in all aspects. Grade II trees, consisting of 26 species (e.g Pinus tabuliformis, Paulownia fortunei, Ligustrum × vicaryi), had the second-highest comprehensive score. Moreover, Grade III trees, encompassing 12 species (e.g Acer mono, Cedrus deodara, Magnolia denudata), exhibited lower comprehensive scores. The extensive use of Grade I and II tree species is recommended in the implementation of low-carbon greening projects in the Bohai Bay region, while Grade III tree species should be judiciously utilized. The findings of this research can serve as a valuable resource for the scientific identification of tree species that are suitable for urban park green spaces in the Bohai Bay region, which is characterized by predominantly saline and alkaline soil. Additionally, the development of an evaluation system can guide the selection of low-carbon tree species when evaluating other types of saline and alkaline lands.

Empirical Analysis of a Super-SBM-Based Framework for Wetland Carbon Stock Safety Assessment

With climate change and urbanization expansion, wetlands, which are some of the largest carbon stocks in the world, are facing threats such as shrinking areas and declining carbon sequestration capacities. Wetland carbon stocks are at risk of being transformed into carbon sources, especially those of wetlands with strong land use–natural resource conservation conflict. Moreover, there is a lack of well-established indicators for evaluating the health of wetland carbon stocks. To address this issue, we proposed a novel framework for the safety assessment of wetland carbon stocks using the Super Slack-Based Measure (Super-SBM), and we then conducted an empirical study on the Quanzhou Bay Estuary Wetland (QBEW). This framework integrates the unexpected output indicator (i.e., carbon emissions), the expected output indicators, including the GDP per capita and carbon stock estimates calculated via machine learning (ML)-based remote sensing inversion, and the input indicators, such as environmental governance investigations, climate conditions, socio-economic activities, and resource utilization. The results show that the annual average safety assessment for carbon pools in the QBEW was a meager 0.29 in 2015, signaling a very poor state, likely due to inadequate inputs or excessive unexpected outputs. However, there has been a substantial improvement since then, as evidenced by the fact that all the safety assessments have exceeded the threshold of 1 from 2018 onwards, reflecting a transition to a “weakly effective” status within a safe and acceptable range. Moreover, our investigation employing the Super-SBM model to calculate the “slack variables” yielded valuable insights into optimization strategies. This research advances the field by establishing a safety measurement framework for wetland carbon pools that leverages efficiency assessment methods, thereby offering a quantitative safeguard mechanism that supports the achievement of the “3060” dual-carbon target.

Application of remote sensing methods for monitoring extent, condition and blue carbon storage in salt marshes

Salt marshes are fragile coastal ecosystems that provide a wide range of ecosystem services, including carbon sequestration and storage. Despite the importance of salt marshes for blue carbon sequestration, few studies have been done on blue carbon monitoring using satellite remote sensing techniques. This study arose to fill this knowledge gap, and aimed to determine the amount of blue carbon sequestered in salt marshes by analyzing the particular case of the Pancas salt marsh (Tagus Estuary, Portugal). To achieve this, the extent and condition of the Pancas salt marsh were assessed using remote sensing methods, by establishing a methodology that effectively identified and validated its extent based on Sentinel-2 imagery from 2016 to 2022. This method involves generating a reference salt marsh extent map followed by mapping salt marsh extent through four Vegetation Indices (VI) from Sentinel-2 data to compare and thus validate the salt marsh extent based on the information provided by the satellite. Considering the extent of the salt marsh and the changes it has undergone over the 7 years studied, together with reference values for sequestered carbon in the salt marsh sediments, approximate values for sequestered blue carbon were determined. The results highlighted the validation of Normalised Difference Vegetation Index (NDVI) as the best-performing VI for this study and as a proxy for the condition of the salt marsh in terms of the spatial and temporal distribution of its aboveground biomass. It was also verified that the salt marsh expanded its frontal region by 0.22 km2 between 2016 and 2022, while certain areas of high marsh have suffered dieback. Concerning sequestered carbon, an increase of 508.2 tonnes since 2016 was quantified, corresponding to 66500 tonnes of blue carbon stored for 2022. Our study revealed the intrinsic relationship between the extent of a salt marsh and its carbon sequestration capacity highlighting the importance of future application of more remote sensing techniques, to emphasize the significant role of these ecosystems in carbon sequestration and climate change mitigation.

Which Provinces Will Be the Beneficiaries of Forestry Carbon Sink Trade? A Study on the Carbon Intensity–Carbon Sink Assessment Model in China

Carbon emissions pose a significant challenge to sustainable development, particularly for China, which is the world’s largest emerging economy and is under pressure to achieve carbon neutrality and reduce emissions amid escalating human activities. The variation in economic development levels and carbon sequestration capacities among its provinces poses a significant hurdle. However, previous research has not adequately examined this dual discrepancy from the perspective of spatial heterogeneity, resulting in a lack of differentiated management of forest carbon sinks across diverse regions. Therefore, to mitigate this discrepancy, this study presents an assessment methodology that analyzes over 100 types of natural and plantation forests using forest age and biomass expansion factors. This study presents a model that can significantly support the efforts of both China and the whole world to achieve carbon neutrality through the improved management of forest carbon sinks. This approach facilitates the assessment of carbon offsets required to meet reduction targets, the development of a provincial framework for carbon intensity and sequestration, and the exploration of their potential for trading markets. Analysis is conducted using MATLAB. Key achievements of this study include the following: (1) The collection of a comprehensive carbon stock dataset for 50 natural and 57 plantation forest types in 31 provinces from 2009 to 2018, highlighting the significant role of new forests in carbon sequestration. (2) The development of a provincial carbon status scoring system that categorizes provinces as carbon-negative, carbon-balancing, or carbon-positive based on local forest sink data and carbon credit demand. (3) The formulation of the carbon intensity–carbon sink assessment (CISA) model, which suggests that provinces with middle- to upper-middle-level economies may have a prolonged need for carbon sink credits during their peak carbon phase. Furthermore, the results show that carbon trading may benefit Guangxi and Yunnan, but may also bring opportunities and risks to Hunan and Hubei. To address regional imbalances, this study advocates tailored policies: carbon-negative and carbon-balancing provinces should enhance carbon sink management, while carbon-positive provinces must focus on energy structure transformation to achieve sustainable development goals.

Biogeochemical factors regulating photosynthetically dissolved organic carbon produced by phytoplankton in the Taiwan Strait

The distribution and mechanisms of photosynthetically dissolved organic carbon (PDOC) released by marine phytoplankton are frequently neglected and inadequately understood because most studies on carbon sequestration capacity have focused on photosynthetic particulate organic carbon. In this study, percentage extracellular release (PER) and its environmental influencing factors were investigated for 10 cruises in the Taiwan Strait during 2006–2023. The results indicated that the PER increased horizontally from the nearshore to the off-shelf and vertically from the surface to the bottom within the euphotic zone. PER tends to be low in eutrophic waters such as upwellings and estuaries and high in oligotrophic waters. The study revealed that the average contribution of PDOC to total primary productivity (TPP) in the Taiwan Strait could reach 18.2 ± 11.7%, which is similar to the previously estimated global oceanic values. PDOC production satisfied approximately 25% the carbon requirements of heterotropic bacteria (HB). A detailed analysis of the PER combined with model simulations proved that the distribution of the PER in the Taiwan Strait was caused by the joint contribution of irradiance, size-fractionated phytoplankton, and nutrient stoichiometry. Our results contradict the view that the PER is a constant factor that is unaffected by TPP. However, there was a significant negative correlation between the PER and TPP. The PDOC was always lower than the bacterial carbon demand for a broad range of bacterial growth efficiencies, suggesting a weak coupling between phytoplankton exudation and bacterial metabolism. This challenges the idea that there is a well-coupled relationship between bacteria and phytoplankton present on the continental shelf. These findings indicate significant discrepancies in PDOC mechanisms and the quantitative importance of nearshore eutrophic and off-shelf oligotrophic environments. Consequently, it is unwise to use uniform PERs without differentiation under trophic conditions when reevaluating and appraising marine carbon fixation.

Enhancing salt marshes monitoring: Estimating biomass with drone-derived habitat-specific models

Salt marshes play a vital role in biodiversity conservation, coastal protection, and carbon sequestration. Estimating aboveground biomass (AGB) is crucial for quantifying the carbon sequestration capacity of the system. However, traditional fieldwork methods are time-consuming, demanding, and detrimental to marsh ecosystems. In this study, we propose utilizing low-altitude remote sensing techniques to collect high-resolution LiDAR and multispectral (MS) data for biomass assessment. With these datasets, we characterized salt marsh vegetation habitats through the analysis of vegetation indices (VIs) variability. LiDAR high-resolution topographic information aids in evaluating habitat distribution. Moreover, the Anthocyanin Reflectance Index 2 (ARI2), combined with the Digital Surface Model, allows for the identification and separation of the two habitats with distinct dominant species (Sarcocornia spp. and Sporobolus maritimus). The analysis of the annual cycle of VIs reveals the presence of seasonality. However, the VIs for the two vegetation classes exhibit dissimilar seasonal changes, indicating distinct growth mechanisms for each. Biomass models are created for each season in the annual cycle. Habitat-specific models exhibit higher precision (up to 99%) than models that treat species uniformly. Depending on whether the marsh is considered as a whole or separated into dominant habitats, differences in biomass estimation trends are observed. This implies that the two dominant species exhibit varying behaviours throughout the year, contributing to diverse biomass production. The study reveals a seasonal pattern in the total AGB, with the highest biomass value in summer and the lowest peak in spring, with annual variation accounting for only 9% of total output. The reduced AGB value in spring may be due to increased soil salinity and stress. The use of LiDAR and MS data from an unmanned aerial vehicle (UAV) is crucial for accurately distinguishing primary marsh habitats and creating detailed biomass models, with unprecedented accuracy. This method is user-friendly, repeatable, and cost-effective, enabling the study of salt marshes, evolutionary trends, and climate change response requiring less fieldwork.

Management and liming-induced changes in organo-Al/Fe complexes and amorphous mineral-associated organic carbon: Implications for carbon sequestration in volcanic soils

Amorphous mineral-associated organic carbon (AMAOC) and organo-Al/Fe complexes (Cp) play crucial roles in soil carbon (C) sequestration in volcanic soils. This study investigated the effects of land use management and liming on the C sequestration capacity of a young allophanic Andisol and old halloysitic-kaolinitic volcanic Ultisol sampled at 0–10 and 10–20 cm depth. This study was designed to test two hypotheses: (1) management and liming affect the C sequestration capacity of Andisol by reducing Cp and increasing AMAOC to offset Cp losses, and (2) they do not significantly affect the carbon sequestration capacity of Ultisol because of its more crystalline mineral forms and reduced amount of Cp. This study was conducted using a selective dissolution technique and density fractionation with agricultural soils and forests as control soils. After 43 years of intensive management and liming, the soil organic carbon (SOC) content decreased by 32% in the topsoil compared to the original native forest soil (178 ± 2 g kg−1 soil), mainly in the particulate organic matter (POM) fraction, which decreased by 74% compared to the native forest soil (61 ± 9 g kg−1 soil). However, Cp decreased only by 40% compared to the forest soil (62 ± 1 g kg−1 soil) from pHKCl 4.8–5.0, and AMAOC increased in 17% in the topsoil and 64% in the subsoil, supporting the first hypothesis of this study. In the cultivated Ultisol, SOC decreased by 35% due to the POM fraction, and mineral-associated organic C (MAOC) decreased by 37% compared to the forest soil (38 ± 7 g kg−1 soil). These results partially support the second hypothesis because the crystalline clay minerals from which MAOC originated remained unchanged and were strongly correlated with SOC. The mass balance of both soils indicated that the stable C losses from native forest soils were < 14%. These results highlight the importance of different C sequestration mechanisms to compensate for SOC losses in the young allophanic Andisol and old volcanic Ultisol. Our findings imply that both mechanisms can be used to estimate the C sequestration capcity in similar soil types.

Seagrass decline weakens sediment organic carbon stability

Seagrass meadows are globally recognized as critical natural carbon sinks, commonly known as ‘blue carbon’. However, seagrass decline attributed to escalating human activities and climate change, significantly influences their carbon sequestration capacity. A key aspect in comprehending the impact of seagrass decline on carbon sequestration is understanding how degradation affects the stored blue carbon, primarily consisting of sediment organic carbon (SOC). While it is widely acknowledged that seagrass decline affects the input of organic carbon, little is known about its impact on SOC pool stability. To address this knowledge, we examined variations in total SOC and recalcitrant SOC (RSOC) at a depth of 15 cm in nine seagrass meadows located on the coast of Southern China. Our findings revealed that the ratio of RSOC to SOC (RSOC/SOC) ranged from 27 % to 91 % in the seagrass meadows, and the RSOC/SOC increased slightly with depth. Comparing different seagrass species, we observed that SOC and RSOC stocks were 1.94 and 3.19-fold higher under Halophila beccarii and Halophila ovalis meadows compared to Thalassia hemprichii and Enhalus acoroides meadows. Redundancy and correlation analyses indicated that SOC and RSOC content and stock, as well as the RSOC/SOC ratio, decreased with declining seagrass shoot density, biomass, and coverage. This implies that the loss of seagrass, caused by human activities and climate change, results in a reduction in carbon sequestration stability. Further, the RSOC decreased by 15 %, 29 %, and 40 % under unvegetated areas compared to adjacent Halophila spp., T. hemprichii and E. acoroides meadows, respectively. Given the anticipated acceleration of seagrass decline due to climate change and increasing coastal development, our study provides timely information for developing coastal carbon protection strategies. These strategies should focus on preserving seagrass and restoring damaged seagrass meadows, to maximize their carbon sequestration capacity.

No effect of invasive tree species on aboveground biomass increments of oaks and pines in temperate forests

Prunus serotina and Robinia pseudoacacia are the most widespread invasive trees in Central Europe. In addition, according to climate models, decreased growth of many economically and ecologically important native trees will likely be observed in the future. We aimed to assess the impact of these two neophytes, which differ in the biomass range and nitrogen-fixing abilities observed in Central European conditions, on the relative aboveground biomass increments of native oaks Quercus robur and Q. petraea and Scots pine Pinus sylvestris. We aimed to increase our understanding of the relationship between facilitation and competition between woody alien species and overstory native trees. We established 72 circular plots (0.05 ha) in two different forest habitat types and stands varying in age in western Poland. We chose plots with different abundances of the studied neophytes to determine how effects scaled along the quantitative invasion gradient. Furthermore, we collected growth cores of the studied native species, and we calculated aboveground biomass increments at the tree and stand levels. Then, we used generalized linear mixed-effects models to assess the impact of invasive species abundances on relative aboveground biomass increments of native tree species. We did not find a biologically or statistically significant impact of invasive R. pseudoacacia or P. serotina on the relative aboveground biomass increments of native oaks and pines along the quantitative gradient of invader biomass or on the proportion of total stand biomass accounted for by invaders. The neophytes did not act as native tree growth stimulators but also did not compete with them for resources, which would escalate the negative impact of climate change on pines and oaks. The neophytes should not significantly modify the carbon sequestration capacity of the native species. Our work combines elements of the per capita effect of invasion with research on mixed forest management.

Submerged macrophyte restoration enhanced microbial carbon utilization in shallow lakes

Submerged macrophytes are integral to the functioning of shallow lakes through their interaction with microorganisms. However, we have a limited understanding of how microbial communities in shallow lakes respond when macrophytes are restored after being historically extirpated. Here, we explored the interactions between prokaryotic communities and carbon utilization in two lakes where submerged macrophytes were restored. We found restoration reduced total carbon in sediment by 8.9 %–27.9 % and total organic carbon by 16.7 %–36.9 % relative to control treatment, but had no effects on carbon content in the overlying water. Sediment microbial communities were more sensitive to restoration than planktonic microbes and showed enhanced utilization of simple carbon substrates, such as Tween 40, after restoration. The increase in carbon utilization was attributed to declines in the relative abundance of some genera, such as Saccharicenans and Desertimonas, which were found weakly associated with the utilization of different carbon substrates. These genera likely competed with microbes with high carbon utilization in restored areas, such as Lubomirskia. Our findings highlight how restoring submerged macrophytes can enhance microbial carbon utilization and provide guidance to improve the carbon sequestration capacity of restored shallow lakes.

Mixing of pine and arbuscular mycorrhizal tree species changed soil organic carbon storage by affecting soil microbial characteristics

Pure and mixed pine forests are found all over the world. The mycorrhizal type affects soil microbial activity and carbon sequestration capacity in pure forests. However, the effects of mycorrhizal type on microbial characteristics and carbon sequestration capacity in pine mixed forests remain untested. Further, making it difficult to predict carbon storage of the conversion from pure pine forests to mixed forests at larger scales. Herein, a meta-analysis showed that the contents of soil microbial biomass, mineral-associated organic carbon, and soil organic carbon in pine mixed forests with introduced arbuscular mycorrhizal tree species (PMAM) increased by 26.41 %, 58.55 %, and 27.41 %, respectively, compared to pure pine forests, whereas those of pine mixed forests without arbuscular mycorrhizal tree species (PMEcM) remained unchanged. Furthermore, the effect size of microbial biomass, mineral-associated organic carbon and organic carbon contents in subsoil of PMAM are 56.48 %, 78.49 % and 43.05 %, respectively, which are higher than those in topsoil. The improvement of carbon sinks throughout the PMAM soil profile is positively correlated with increases in microbial biomass and mineral-associated organic carbon in subsoil, according to regression analysis and structural equation modelling. In summary, these results highlight that the positive effects of introducing arbuscular mycorrhizal tree species rather than ectomycorrhizal tree species into pure pine forests on soil microbial biomass and carbon sequestration. The positive link between microbial biomass, mineral-associated organic carbon, and soil organic carbon suggests an underlying mechanism for how soil microorganisms store carbon in pine mixed forests. Nevertheless, our findings also imply that the soil carbon pool of PMAM may be vulnerable under climate change. Based on the above findings, we propose that incorporating mycorrhizal type of tree species and soil thickness into mixed forests management and biodiversity conservation.

Exploring the Effect of Moisture on CO2 Diffusion and Particle Cementation in Carbonated Steel Slag

The study of the mechanisms affecting the preparation parameters of carbonated steel slag is of great significance for the development of carbon sequestration materials. In order to elucidate the mechanism of the influence of moisture on CO2 diffusion and particle cementation in steel slag, the effects of different water–solid ratios and water contents on the mechanical properties, carbonation products, and pore structure of steel slag after carbonation were investigated. The results show that increasing the water–solid ratio of steel slag can control the larger initial porosity and improve the carbon sequestration capacity of steel slag, but it will reduce the mechanical properties. The carbonation process relies on pores for CO2 diffusion and also requires a certain level of moisture for Ca2+ dissolution and diffusion. Increasing the water content enhances particle cementation and carbonation capacity in steel slag specimens; however, excessive water hinders CO2 diffusion. Reducing the water content can increase the carbonation depth but may compromise gelling and carbon sequestration ability. Therefore, achieving a balance is crucial in controlling the water content. The compressive strength of the steel slag with suitable moisture and initial porosity can reach 118.7 MPa, and 217.2 kg CO2 eq./t steel slag can be sequestered.

Carbonation curing of magnesium-coal slag solid waste backfill material: Study on properties of flow, mechanics and carbon sequestration

To expedite the achievement of the ''30–60 double carbon'' goal, it is imperative to create a novel, low-carbon, cost-effective, and sustainable backfill material for mining purposes. Against this background, this paper investigates the workability, carbonation performance and carbon sequestration capacity of coal gangue (CG), magnesium slag (MS) and fly ash (FA) as magnesium coal slag solid waste backfill material. The results of the study show that: (1) The rheological properties of the CFM fresh slurry conform to the Herschel-Balkley (H-B) model, and its flowability meets the requirements of mine backfill transport. With increasing MS content, the yield stress, apparent viscosity, thixotropy and shear thickening of CFM fresh slurry increase, and the micro-slump and diffusion diameter decrease. (2) Carbonation curing can effectively improve the early UCS of CFM. The highest UCS of CFM was 8.854 MPa after 7 days of carbonation curing, which was 27.84 times higher than that of standard curing. In addition, the UCS of CFM increased with the increase of curing age and MS content. (3) CFM produces a large number of carbonation products such as calcium carbonate after carbonation curing, which makes its microstructure denser. (4) CFM can absorb up to 14.55 % of CO2 after carbonation. (5) The volume stability of CFM is significantly improved after carbonation curing. In summary, CFM is not only a new type of low-cost, low-carbon and sustainable solid waste backfill material, but its practical application in the field of mine backfilling also has great potential for the realization of magnesium coal slag solid waste resource utilization and CO2 sequestration.

Navigating Synergies: A Comprehensive Review of Agroforestry System and Agronomy Crops

Agroforestry, the integration of trees with agricultural or livestock systems, holds significant promise for sustainable land management and addressing various environmental challenges. This comprehensive review explores the multifaceted benefits and challenges associated with agroforestry systems, focusing on their interactions with agronomy crops. We delve into the ecological, socio-economic, and climate-related dimensions of agroforestry, highlighting its potential to enhance productivity, conserve resources, and mitigate climate change impacts. The review begins by examining the historical context and conceptual foundations of agroforestry, elucidating its diverse array of products and services. Through case studies and empirical research, we explore the ecological benefits of integrating trees with crop production, emphasizing improvements in soil fertility, water quality, and biodiversity conservation. Furthermore, we discuss the role of agroforestry in climate change adaptation and mitigation, including its capacity for carbon sequestration, soil restoration, and resilience-building in the face of extreme weather events. A critical analysis of agroforestry's implications for agronomy crops reveals both opportunities and challenges. While agroforestry systems have shown potential to enhance crop yields, improve soil health, and diversify income sources, they also present complexities related to competition for resources and management practices. Insights from studies conducted in various agro-ecological contexts provide valuable guidance for optimizing the design and implementation of agroforestry systems to maximize their benefits for agronomy crops. This review underscores the importance of interdisciplinary collaboration and knowledge exchange in advancing agroforestry research and practice. By integrating principles from agronomy, ecology, economics, and forestry, we can develop innovative strategies to harness the full potential of agroforestry for sustainable agriculture and environmental conservation.

Comparative Carbon Stock Potential of Indigenous Agroforestry Systems in Silte Wereda, Southern Ethiopia

Agroforestry system (AFS) is described as one of the promising mitigation options for climate change through its high carbon sequestration capacity. This study was conducted in Silite District; Southern Ethiopia to assess the unaccounted carbon stock potential of selected traditional agroforestry systems. The study assessed the carbon stock potential of AFS biomass and soil carbon pools. Biomass and soil samples were taken from temporary plots laid for this study, 20 × 20 m for home garden, 50 × 100 m for parkland, and 10 × 10 m for woodlot AFS. Height (H) and diameter at breast height (DBH) were taken from the sample plots to estimate biomass carbon. Litter, herb, and grass samples were collected from 1 m2 quadrant within the main plot. The findings show that the total biomass carbon ranged from (1.28-7 Mg ha -1) though there was no significant difference among the systems and higher biomass carbon was attributed by parkland AFS while the lowest was woodlot. A significantly higher amount of SOC was recorded in home garden AFS along the two depths (82.5 Mg ha -1) than the other two systems and the lowest was attributed to parkland (41.7 Mg ha -1). Therefore, this traditional AFS should be supported for their contributions in climate change mitigation schemes as they can sequester a reasonable amount of carbon

Effect mechanism of phosphorous-containing additives on carbon structure evolution and biochar stability enhancement

The regulation of the pyrolysis process is a key step in increasing the carbon sequestration capacity of biochar. The effect of K3PO4 addition on the yield, chemical composition, characteristic functional groups, macromolecular skeleton, graphite crystallites, and stability of biochar was studied in this paper using two-dimensional infrared correlation spectroscopy (2D-PCIS), X-ray photoelectron spectroscopy, Raman spectrum, and other characterization methods combined with thermal/chemical oxidation analysis. It is discovered that adding K3PO4 may effectively minimize the graphitization temperature range and increase biochar's yield, aromaticity, H/C ratio, and proportion of refractory/recalcitrant organic carbon. The 2D-PCIS and Raman analysis revealed that K3PO4 mostly promoted the dehydrogenation and polycondensation process of the aromatic rings in the char precursor, transforming the amorphous carbon structure of biochar into an ordered turbostratic microcrystalline structure. K3PO4 enhanced biochar stability mostly at medium-high temperatures (350 ~ 750℃) by stimulating the transformation of unstable structures of biochar to stable carbon-containing structures or by inhibiting the interaction of its active sites with oxidants through the mineralization process. A 20% phosphorus addition increased biochar's refractory index (R50) by roughly 11%, and it also boosted biochar's oxidation resistance (H2O2 or K2CrO4) efficiency, reducing carbon oxidation loss by up to 7.31%. However, at higher temperatures (> 750 ℃), the doping of phosphorus atoms into the carbon skeleton degraded the biochar structure's stability. The results of this study suggest that using exogenous phosphorus-containing additives is an efficient way to improve the stability of biochar.Graphical abstract

Spatio-Temporal Variation and Future Sustainability of Net Primary Productivity from 2001 to 2021 in Hetao Irrigation District, Inner Mongolia

The Hetao Irrigation District in Inner Mongolia, a vital grain-producing region in northern China, faces growing environmental challenges. Studying net primary productivity (NPP) is essential for understanding spatiotemporal vegetation shifts and guiding locally adapted restoration and management efforts. Utilizing MOD17A3/NPP data, this study applies the Theil–Sen median trend, Mann–Kendall significance, and the Hurst index to scrutinize the spatiotemporal distribution patterns of NPP from 2001 to 2021 and forecast future changes in the area. The findings reveal cyclic temporal trends, forming a “∧” shape with initial increases followed by decreases, notably during the July to August period each year. The multi-year average NPP exhibits a slight upward fluctuation trend, averaging 172.40 gCm−2a−1. Peaks occur approximately every three years, reaching the highest average in 2012 at 218.96 gCm−2a−1. Spatially, NPP distribution stays consistent over the years, influenced by various land cover types, especially cropland, shaping the spatial patterns. Monthly and yearly NPP trends over the 21 years indicate a significant decrease in May and June, with other months mostly showing a non-significant increase. The Hurst index for monthly and yearly NPP changes over 21 years shows relatively high weak anti-persistence. In summary, over the past 21 years, the NPP trend in the study area has not significantly improved and is expected to decline in the future. This study offers data support and a scientific foundation for refining the carbon cycle model, quantifying vegetation carbon sequestration capacity, addressing climate change policies, and striving for carbon peak and neutrality in the Hetao Irrigation District.